The present invention relates to a cleaning solution for removing contaminants from a semiconductor substrate and cleaning method using the same.
As semiconductor devices become more highly integrated, a reduction in their elements is most likely inevitable. However, in all likelihood, not all dimensions will be reduced by the same ratio. For instance, the thickness of an interdielectric layer and wiring film is constrained by potential changes in the entire design since the interdielectric layer and wiring film should maintain minimum pressure resistance, parasitic capacitance, current capacitance, or interconnection resistance. Accordingly, an increase in the aspect ratio of a contact hole formed within an interdielectric layer often results.
The above problem in turn may require one to employ an etching process having a high selectivity ratio. Such an etching process often is problematic in that it may produce an excess of etching byproduct such as, for example, polymers. The layer exposed to such etching is often eroded. For example, in a memory cell area of a dynamic random access memory (DRAM), the process of forming a self-aligned contact (SAC) between gate electrodes often involves a high selectivity ratio between a nitride spacer along the side wall of a gate electrode and an interdielectric layer. The SAC etching process is not only capable of generating a large quantity of polymers, but also often damages the surface of a silicon substrate.
In view of the above, the process for forming the SAC is typically followed by a cleaning process for removing the etching byproduct and damaged film resulting therefrom. In on example, an SAC cleaning includes the use of standard cleaning solution 1 (SC1) which contains ammonium hydroxide, hydrogen peroxide, and water in a respective ratio of 1:4:20 by volume, followed by deionized water diluted hydrogen fluoride solution rinse. However, this conventional cleaning solution often has an undesirably high etching rate for an impurity doped interdielectric layer such as a borophosphorous silicate glass (BPSG) layer. As a result, the BPSG layer is usually also etched away in the cleaning process for removing polymer and damaged layers. Such a drawback makes adjustment of the critical dimensions of the SAC difficult, and, more significantly, it may cause an undesirable electrical short between adjacent SACs.
In an attempt to solve the above problems, it is an objective of the present invention to provide cleaning solutions for selectively removing contaminants from semiconductor substrates with respect to impurity doped dielectric layers.
It is another objective of the present invention to provide cleaning methods for removing contaminants from the surfaces of semiconductor substrates using the above cleaning solutions.
According to one aspect of the invention, a cleaning solution for removing at least one contaminant from a semiconductor substrate is provided. The cleaning solution comprises from about 0.08 to about 0.1 percent by weight of hydrogen fluoride; from about 0.5 to about 0.6 percent by weight of ammonium fluoride; from about 24.9 to about 49.7 percent by weight of hydrogen peroxide; and from about 49.6 to about 74.5 percent by weight of water.
According to another aspect of the invention, a method for removing at least one contaminant from a semiconductor substrate and comprises contacting the exposed surface of the semiconductor substrate with a cleaning solution comprising from about 0.08 to about 0.1 percent by weight of hydrogen fluoride; from about 0.5 to about 0.6 percent by weight of ammonium fluoride; from about 24.9 to about 49.7 percent by weight of hydrogen peroxide; and from about 49.6 to about 74.5 percent by weight of water to remove the at least one contaminant from the exposed surface of the semiconductor substrate.